Custom heatmap 3D texture
I quite didn't understand the meaning of your Heat map so I created a not-so-complex procedural material, which would consist of 3-4 nodes based on your heat map.

1] Depth Map : This map is based on height, if u want this kind of material then use the top three nodes
nodes 


2] Fake Heat Map : This is a fake heat map based on distance from the
camera, a very common filter.



Ahh! I nearly forgot, you can also use the layer weight node to get
the faces facing the camera. Like This :